JP7418427B2 - Cotton-based elastic yarn for making eco-friendly elastic fabrics - Google Patents

Description

Description The present invention relates to a method for making cotton-based elastic yarns and also to environmentally friendly elastic fabrics made therefrom.

BACKGROUND OF THE INVENTION - TECHNICAL ISSUES Stretch fabrics are used in a wide variety of applications. In particular, stretch fabrics are used to produce garments that do not restrict or accommodate the movements of the user's limbs, creating a comfortable sensation for the user. This feature is particularly appreciated in underwear or sports and gym clothing, but is also useful in everyday life situations such as sitting in a car, walking, and whenever you bend a joint. Stretch fabrics are also advantageously used to provide close-fitting coverings for rounded objects, such as sofas and armchairs.

The characteristics of stretch fabrics depend on the high elasticity of the stretch threads used in their manufacture. For example, US 2,992,150, US 3,380,244, EP 2,145,034 and EP 2,638,192 describe elastic ring-spun yarns etc. in which the elastic filaments are surrounded by a fiber sheath comprising a mass of synthetic or natural staple fibers. . In some cases cotton fibers are used.

Additionally, denim-type stretch fabrics have been known and highly valued for several years. With these fabrics, the above-mentioned advantages of stretch fabrics can be extended to jeans garments. For example, EP2145034 and EP2638192 relate to these fabrics.

However, the elastic threads conventionally used to make stretchable threads are made from synthetic materials, and in particular the above-mentioned patent documents relate to polyurethane or polyolefin elastic materials. Therefore, articles containing fabrics made of cotton and elastic yarns cannot be easily disposed of, and in particular they cannot be disposed of by composting. Additionally, synthetic elastic yarns can cause allergies in some skin-sensitive people who wear clothing made from fabrics containing them.

To alleviate the above drawbacks, an alternative to synthetic elastic yarns could be the use of natural rubber elastic yarns. However, commercially available equipment can only accept very thin elastic yarns, and currently available natural rubber yarns have too high a linear mass density to be stretchable by currently preferred spinning techniques such as ring spinning or open-end spinning. It cannot be used to make thread.

Therefore, the present invention aims to provide a method for making elastic yarns from elastic fibers and cotton-based yarns, in which natural rubber fibers can be used as elastic fibers, and the above-mentioned natural rubber fibers are commercially available. has a metric count that is generally available, thus overcoming the above-mentioned limitations of conventional spinning methods.

Furthermore, it is an object of the present invention to eliminate problems due to insufficient elastic recovery of elastic yarns, for example after stretching and subsequent release of the fabric, during the manufacture and normal use of garments and other articles made therefrom. It is an object of the present invention to provide a method for producing such a stretchable yarn, which can produce a stretchable fabric free of problems caused by inelastic deformation that occurs even when the yarn is used.

Furthermore, a particular object of the invention is that the elastic yarn can be unwound from a spool containing an end flange without requiring periodic adjustment of the tensile forces acting on the elastic yarn, and It is an object of the present invention to provide a method for producing elastic yarns that can be delivered to a processing unit at a draw ratio.

Another particular object of the invention is to provide such elastic yarns and denim-type fabrics made therefrom.

These and other objects are achieved by the method defined by the appended claim 1. Exemplary specific embodiments of the invention are defined by the dependent claims. The above objects are also achieved by yarns and fabrics as defined by claims 15 and 16, respectively.

According to the present invention, the method for making an elastic core yarn comprises:
pre-positioning a source of an elastic core comprising rubber fibers obtained by extruding natural rubber, i.e. a natural latex containing more than 80% cis-1,4-polyisoprene, wherein the elastic fibers are pre-positioning having a linear mass density set between 200 dtex and 1000 dtex;
- pre-positioning at least one coated yarn comprising cotton at a weight percentage of more than 50%;
The covered yarn has a linear mass density set between 6Nm and 100Nm,
pre-positioning, wherein said covered yarn is twisted in an initial twist direction selected between "Z" and "S";
- transporting the elastic core and the above-mentioned coated yarn at their respective predetermined transport speeds to a collection spool, comprising:
The conveyance speed of the elastic core is
・From the initial velocity at the source of the elastic core,
- ranging up to a final velocity of at least twice the initial velocity at the collection spool;
the step of conveying is carried out in such a way that the covered yarn reaches laterally in the vicinity of the elastic core in the winding space;
- spirally wrapping the coated thread around the elastic core in the winding space, thus obtaining an elastic core thread;
The conveyance speed is set at the step of spirally winding.
・So that the covered yarn is twisted in a final twist direction opposite to the initial twist direction, that is, selected from "S" and "Z", respectively,
- The number T of coils of the covering yarn, set between a predetermined minimum value T ₀ and a predetermined maximum value T ₁ according to the linear mass density Nm, is set around one length unit of the elastic core yarn. selected so that it can be wrapped around the
The wrap space is a protected space surrounded by a container.

The elastic yarn according to the present invention, whose elasticity is provided by natural rubber yarns with a linear mass density as high as that currently available in the industry, is an elastic core yarn and is not suggested by the cited prior art. It is not a yarn obtained by spinning techniques such as ring spinning or open-end spinning. The invention disclosed above solves several typical problems that may otherwise be involved in the manufacture of elastic core yarns, as explained below.

The pre-placed covered yarns can be first Z-twisted, which is the most commercially available twisting direction. According to the invention, the winding step consists of forming a coil around the elastic core while the covering yarn is reverse twisted, i.e. twisted in the direction opposite to the initial twisting direction, initially reducing the number of Z twists to zero. and then carried out to form a predetermined number of S twists per unit of length of the elastic core yarn. In this case, the initial or first twist direction is "Z" and the last or second twist direction is "S". Alternatively, of course, the covered yarn can be first S-twisted, and the winding step is such that the covered yarn is reverse-twisted, forming a coil around the elastic core, initially reducing the number of S-twists to zero. and then carried out to form a predetermined number of Z twists per unit of length of the elastic core yarn. In this case, the initial or first twist direction is "S" and the last or second twist direction is "Z".

Thus, while being wound around the elastic core, the coated yarn first loses its twist in the initial twist direction (eg, a Z twist) and then undergoes a twist in the opposite direction (in this example, an S twist). Conversely, if the winding step is carried out by increasing the number of twists in the initial twist direction, the coated yarn will quickly become too "clinged" together, before the appropriate desired number of coils are wound around the elastic core. There is a possibility of breakage.

Therefore, the method according to the invention forms more coils per unit of length of the elastic core yarn without dangerously approaching or reaching the critical stability limit of the covered yarn, and with excessive torsion levels, the elastic core yarn to prevent any risk of destroying it.

If the number of coils per unit length is greater than the above-mentioned minimum value, a sufficiently closely packed coil structure is obtained to cause the coils to undergo a substantially regular elastic recovery. Therefore, the large number of coils per unit of length, and the resulting highly filled structure that can be safely reached by the method according to the invention, makes the coils substantially smaller when the yarn is drawn and then released. to its original unstretched configuration. This allows the elastic core yarn to penetrate between adjacent coils of covered yarn while being drawn and remains protruding from the elastic core yarn after being released, making it possible for any fabricated from elastic core yarn to Prevent significant deterioration of the appearance of the fabric and its elastic properties.

Furthermore, in the method according to the invention, the coated yarn, after losing its twist in the initial twist direction and before undergoing any twist in the final twist direction, has discontinuous cotton fibers and potential fiber close contact of different materials. Crosses the zero torsion state where the torsion is small or absent. As is well known, the closeness between fibers and thus the strength of articles made of discontinuous fibers is primarily ensured by twisting such fibers together to obtain yarns. With the zero torsion conditions provided by this method, the potential for the covering yarn to come apart while being wrapped around the elastic core can be a problem.

However, the protection of the winding space provided by the container limits or substantially suppresses the friction of the covered yarn with the air, thus preventing the covered yarn from coming apart as it traverses the zero torsion condition described above. avoid the risk of becoming

The method according to the invention therefore makes it possible to use elastic natural rubber threads with a higher linear mass density than is currently available on the market, ie typically between 200 and 500 dtex. Therefore, thanks to this method, it is possible to obtain elastic core yarns suitable for making elastic fabrics that advantageously contain natural rubber instead of synthetic elastic yarns other than cotton, and therefore these elastic fabrics Contains only environmentally friendly materials, especially compostable materials. Thus, it is possible to obtain articles that can be turned into compost at the end of their service life or in any case decompose naturally.

Furthermore, such stretch fabrics are particularly suitable for people with sensitive skin compared to the synthetic polymer fibers from which denim-type stretch fabrics are usually manufactured.

As is well known, the metric count Nm is an indirect measure of the linear density of a fabric (its reciprocal) and is defined as the number of kilometers corresponding to 1 Kg of yarn or filament. In other words, the metric number is expressed in Km/Kg. An alternative linear density unit for textiles is the tex, which in turn is the mass in grams corresponding to 1 Km of thread or filament, or its submultiples such as dtex (0.1 tex).

Twists per meter is directly counted as the number of reverse torsions required to completely remove the twist of a given length of twisted yarn placed between two fixed points at a given initial tensile extension. means the number of twists that can be made. In particular, the predetermined length and initial tensile extension are selected according to ISO 2061.

In particular, the predetermined minimum value T ₀ is the value that for each linear mass density value Nm shown in the respective row of Table 1 is written in the same row and column starting with "T ₀ " of this table, respectively; For the above-mentioned linear mass density value Nm between the values shown in each adjacent row, _the minimum _value T ₀ linearly Obtained by interpolation.

In particular, the predetermined maximum value T ₁ is the value that, for each linear mass density value Nm shown in the respective row of Table 1, is written in the same row of the table and in the column starting with "T ₁ ", respectively; _For the above-mentioned linear mass density value _Nm between the values shown in adjacent rows _of obtained by doing. With such a number of coils per unit length, a coil structure is obtained that is not so tightly packed as to degrade the elastic properties of the elastic core yarn and thus any fabric made therefrom.

For each linear mass density value Nm, the number of coils per unit of length T is given by:
T=KNm ^0.425
can be provided by
where K is a number set between 75 and 290, which substantially corresponds to the above-mentioned minimum and maximum values T ₀ and T ₁ of the above-mentioned number of wound coils, respectively.

Preferably, K is set between 90 and 250, more preferably between 120 and 220.

Preferably, the number of coils T per unit of length is set from the median value T ₂ minus 10% to the same median value T ₂ plus 10%, the median value T ₂ being several metric values Nm is shown in Table 2 and is obtained by linear interpolation of closely spaced _T2 values for intermediate metric numbers.

Covered yarns can be single layer yarns, double layer yarns, and yarns with three or more layers.

Advantageously, the step of conveying the elastic core and coated yarn to the collection spool comprises:
- moving the elastic core and the covering yarn along the sides, respectively, through a longitudinal through-hole of a rotating hollow cylinder rotating at a predetermined rotational speed, the longitudinal through-hole being a part of the elastic core; having an inlet end opening and an outlet end opening for;
- passing the elastic core and the above-mentioned covering yarn at a predetermined distance therefrom through an orifice facing the outlet end opening of the longitudinal through-cavity of the hollow cylinder;
A winding space is defined between the outlet end opening and the orifice, so that the container has an outlet passage in the orifice and the elastic core, through which the covered yarn passes as the elastic core yarn described above.

More particularly, pre-positioning the source of elastic core includes pre-positioning a first spool of elastic fiber, while pre-positioning the covered yarn comprises pre-positioning a second spool of covered yarn. coaxially attaching the hollow cylinder to the hollow cylinder. The conveying step includes drawing and unwinding the elastic fiber from the first spool at a predetermined unwinding speed equal to the aforementioned conveying speed. The conveying step also includes wrapping the coated yarn around the elastic core and drawing the elastic core outside the orifice, at a selected draw/collection rate to obtain a predetermined draw ratio of the elastic fibers. collecting the elastic core yarn on a third collection spool. In particular, this distraction ratio is set between 2 and 6.

In particular, this method is suitable for hollow spindle twisting machines, e.g. Hamel-type machines that allow a protected balloon configuration, i.e., where the elastic core and covering yarn are enclosed in a container as they meet to form the elastic core yarn. It can be operated on anything.

In particular, the source of the elastic wick may be a spool including a central hub having a friction radius and end flanges having a flange radius, the spool being rotatably disposed about its own first axis and having an elastic Transporting the core includes unwinding the elastic core from the spool. In this case, the intermediate balancing cylinder has a predetermined diameter longer than the flange radius shortened by the hub radius, and its own fixed second axis parallel to the first axis is connected to the spool and the first and The spool is disposed between and in contact with the spool and the motion distribution shaft parallel to the second axis. In this way, the elastic core maintains contact with the intermediate balance cylinder during the unwinding step.

Advantageously, elastic fibers also contain the following components:
- A vulcanizing agent that is sulfur at a weight concentration in natural rubber set at 0.5% to 3.0%;
・Vulcanization accelerator and vulcanization activator,
・Anti-stick agent and
・Antioxidants and
・Contains a stabilizer,
The elastic fibers are obtained from longitudinally cut flat threads of natural rubber so that the elastic fibers are obtained in the form of elastic filaments with the above-mentioned linear mass density.

In an exemplary embodiment, the elastic core includes complementary threads disposed along the elastic fibers. In this way, the friction between the covered yarn and the coils of elastic fibers is significantly reduced, which may be caused by some wearer's movements or postures, or even when manufacturing articles such as clothing from elastic fabrics. , prevents the formation of sagging, substantially inelastic deformations in the fabric due to insufficient elastic recovery after stretching and then releasing the fabric section, which often occurs in garments.

In this case, the step of pre-positioning the source of elastic cores includes the step of pre-positioning a fourth spool of complementary yarn, and the step of conveying the elastic cores includes the step of pre-positioning the source of the elastic cores from the respective first and fourth spools. A friction wheel is provided which includes complementary yarns along with the fibers and where the elastic fibers and complementary yarns converge before being conveyed together into the winding space.

In particular, the complementary yarn is made of a biodegradable material that can be selected from the group consisting of, for example, wool, silk, cotton, flax, hemp, jute, sisal, raffia, ramie.

Complementary threads can be discontinuous or continuous threads. In the latter case, it can be placed parallel to the elastic fiber or interconnected to it, i.e. connection points can be provided at a predetermined distance from each other between the complementary yarn and the elastic fiber, or the elastic fiber for example, to form a covering around it. The continuous complementary yarn may be a single filament continuous yarn or a multifilament continuous yarn, in which case the filaments may be flattened or textured. Preferably, the complementary yarn has a metric count set between 22 dtex and 150 dtex.

Also within the scope of the invention are elastic yarns obtained by the above-described method, and elastic fabrics containing at least a portion of the above-mentioned elastic yarns obtained by the above-described method.

The invention will be illustrated using the following description of exemplary embodiments by way of illustration, but not limitation, with reference to the accompanying drawings, in which: FIG.
1 schematically depicts the steps of helically winding a covered yarn around an elastic core containing elastic fibers to obtain an elastic yarn in the form of an elastic core yarn; FIG. 1 schematically depicts an apparatus for performing the step of helically winding a coated thread around an elastic core in an exemplary embodiment; 1 is a schematic side view of an unwinding unit for unwinding elastic fibers of a twisting element, the unwinding unit including an intermediate balance cylinder; FIG. 1 is a schematic side view of an unwinding unit for unwinding elastic fibers of a twisting element, the unwinding unit including an intermediate balance cylinder; FIG. Figure 3 shows the unwinding unit Figures 3 and 4 at three different moments of the unwinding step, namely the beginning (a), the end (c) and the intermediate moment (b) of the unwinding step. It shows how the minimum, maximum and reference number of coils depends on the metric count of the covering yarn. Figure 2 schematically depicts the step of helically winding a covering yarn around an elastic core comprising complementary yarns in addition to elastic fibers. 8 schematically shows an apparatus for carrying out the step of helically winding the coated yarn around the elastic core of FIG. 7; FIG.

Description of Preferred Exemplary Embodiments Referring to FIG. explained. The method provides for pre-positioning an elastic core 30 comprising elastic fibers 10 made of natural rubber and having a linear mass density typically set between 200 dtex and 1000 dtex. This method also includes a cotton-based coated yarn 40 having a metric count Nm and being twisted in a predetermined initial twist direction which may be "Z" or "S", typically "Z" as available in the industry. including the step of pre-positioning.

The elastic core thread 50 is obtained by a covering step by spirally winding the covering thread 40 around the elastic core 30. In order to achieve the winding, a step is provided for conveying the elastic core 30 and the covered thread 40 at respective speeds v ₁ and v ₂ into the winding space 35 , such that the covered thread 40 crosses the elastic core 30 in a transverse, i.e. tangential direction. , the covering yarn 40 is at a predetermined angle α relative to the elastic core 30 when it reaches the elastic core 30 so as to form a substantially helical covering around the elastic core 30 .

The winding space 35 is typically a closed space, as shown in Figure 2, so that the covered thread 40 limits the friction of the elastic core 30, the covered thread 40, and the thread 50 with air during the winding step. Therefore, upon entering the wrapping space 35, it changes from a substantially linear configuration to a helically wrapped configuration in a reduced turbulence environment.

As also shown in FIG. 2, the step of conveying the elastic core 30 and the covering yarn 40 is controlled by the speed v ₃ at which the elastic core yarn 50 is collected on the collection spool 70. As a result, the covered yarn 40 and the elastic fibers 10 are drawn from their respective sources, which may be storage devices such as spools 41, 51.

As also shown in FIG. 2, in the exemplary embodiment, the step of conveying the elastic core 30 towards the winding space 35 is such that it rotates rapidly around its own axis 63' at a predetermined rotational speed. The elastic core 30 is then conveyed along a substantially linear path. Instead, the step of conveying the covered thread 40 is carried out along the outer surface 62 of the first cylinder 61, preferably along a guide element (not shown) arranged thereon. Preferably, the first cylinder 61 is housed integrally and coaxially within the second hollow cylinder 64 to form the transport unit 60 . The spool 41 of the covered thread 40 is arranged integrally within the second cylindrical body 64, so that the step of conveying the covered thread 40 can be carried out in the gap between the spool 41 and the outer surface of the first cylindrical body 61. It will be held at 65.

In this exemplary embodiment, the winding space 35 is located at the outlet end 69 of the first cylindrical body 61 where the elastic core 30 is delivered and where the elastic core yarn 50 is in a drawn state for being conveyed to the collection spool 70. an orifice 66 preferably disposed along an axis 63' which is released at the The covering of the winding space 35 is made by a preferably axisymmetric wall 67' converging from the inner surface of the second hollow cylinder 64 into an orifice 66, thus forming a container 67, the orifice 66 of which is connected to the winding space 35. This is an exit passage for the elastic core yarn 50 formed within.

The conveying speeds v ₁ and v ₂ (FIG. 1) of the elastic core 30 and the covered yarn 40, respectively, and the rotational speed of the conveying unit 60 are determined by the following values: 40 changes its own twist direction, for example from "Z" to "S", in other words, it is twisted in the final twist direction opposite to the initial twist direction, turning the Z-twist covered yarn 40Z into an S-twist covered yarn. 40S is selected. Furthermore, the speeds v ₁ and v ₂ are such that the number T of coils set between a predetermined minimum value T ₀ and a predetermined maximum value T ₁ is equal to The maximum and minimum values T ₀ , T ₁ are selected to be wound around and depend on the metric count Nm of the covering thread 40 .

The source 51 of the elastic core 30 may be a spool 51 of elastic fibers 10 rotatably disposed about its own axis 52, at the end of a central hub 53 of radius r, as shown in FIG. , a central hub 53 of radius R and end flanges 54. The spool 51 is moved by a motion distribution shaft 58, ie a cylinder 58 which is rotatably arranged around its own axis of rotation 59 throughout the array of aligned twisting units of the twisting machine. For this purpose, the axis of rotation 59 of the motion distribution shaft 58 is parallel to the (common) axis of rotation 52 of the (each) spool 51, and the motion distribution shaft 58 is parallel to the (common) axis of rotation 52 of the (each) spool 51, as also shown in FIG. 51 is placed in contact with the free surface of the unwound elastic fiber 10 in order to rotate it at a prefixed rotational speed.

In a preferred embodiment of the invention, as shown in FIGS. 3-5, an intermediate balance cylinder 56 is provided with an axis 57 of the elastic fiber 10 parallel to the axis 52 of the spool 51 and the axis 59 of the motion distribution shaft 58. It is arranged between the motion distribution shaft 58 and the spool 51 of the twisting unit. More particularly, the intermediate balance cylinder 56 is arranged freely rotatable in contact with the surface of the motion distribution shaft 58 on one side and with the surface of the spool 51 on the other opposite side, i.e. the winding It is placed in contact with the free surface 10 of the returned elastic fiber. The cylinder radius P of the intermediate balance cylinder 56 is longer than the flange radius R and shortened by the hub radius r, i.e. the following relationship P>R-r
is verified.

The shaft 52 of the spool 51 is slidably disposed along a guide 55 that is integrated with the spinning machine. Thus, as the unwinding step progresses, the amount of elastic fibers 10 on the spool 51 decreases, and thus the shaft 52, together with the spool 51, progressively approaches the intermediate balance cylinder 56, as shown in FIG. and thus approaches the motion distribution shaft 58. In a vertical arrangement of the unwinding unit in which the spool 51 is arranged above the motion distribution shaft 58 as in FIGS. 3 and 4, the force of gravity acting on the spool 51 causes the relative Approaching movements are possible. In other cases, but preferably also in this case, spring means, not shown, may advantageously be provided to progressively recall the spool 51 back to the motion distribution shaft 58 as the step of unwinding the elastic fibers 10 progresses. Can be done.

Therefore, as shown in FIG. 5, the elastic filament 10 is always pulled out from the spool 51 by the same distance L=S+2P while being unwound, regardless of the unwinding state of the coil 51, and S (FIG. 3) is , the radius of the motion distribution shaft 58. Thus, as the step of unwinding progresses, if the winding speed v ₃ is kept at a fixed value, the draw ratio of the elastic fiber 10 is kept at a fixed value, preferably between 2 and 6, and in practice In order to keep the number of coils wound around the core at a fixed value, no periodic adjustment of the tensile force acting on the elastic fibers 10 is necessary.

The material of the covering yarn is a cotton-based material, in particular containing at least 50% cotton. For example, the material may be a material commonly used to make denim fabric. Cotton-based coated yarns can be single-layer yarns, double-layer yarns, or even yarns with three or more layers.

FIG. 6 shows, in the form of a curve 81, a predetermined minimum value T ₀ of the number T of coils wound around a unit of length of the elastic core yarn 50 produced for each linear mass density value Nm of the covered yarn 40. FIG. Curve 81 is obtained by interpolating the values in the middle column of Table 1.

The diagram in FIG. 6 also shows, as experience has shown, a curve 82 indicating, for each linear mass density value Nm of the covering yarn 40, the maximum number T ₁ of coils that can be wound without losing the elastic properties of the elastic core yarn 50. shows. Curve 82 is obtained by interpolating the values in the right column of Table 1.

Advantageously, for each value Nm of the metric count of the covering yarn 40, the number T of coils per unit of length of the elastic core yarn 50 is determined by the following formula:
T=KN _m ^0.425
Provided by
where K is a number set between 75 and 290, these values substantially corresponding to curves 83 and 84 in the diagram of FIG. More specifically, K can be set between 90 and 250, more specifically between 120 and 220.

The diagram of FIG. 6 also shows the preferred value of the number of coils per unit of length T, set between ±10% of the central reference value _T2 obtained by interpolating the values of Table 2 corresponding to curve 86. A band 85 corresponding to is shown.

Referring to FIGS. 7 and 8, the elastic core 30 can also include complementary threads 20 disposed along the elastic fibers 10. In this case, the step of pre-positioning the elastic core 30 provides the step of pre-positioning a fourth spool (not shown) of complementary yarn 20, and the step of conveying the elastic core comprises, in addition to the elastic fibers 10, A complementary thread 20 is also included. A friction wheel 15 is also provided in which the elastic fibers 10 and the complementary threads 20 converge before being conveyed together in the central longitudinal direction through its cavity 63 of the first cylindrical hollow body 61 and through its inlet opening 68 can be done.

Preferably, the complementary yarn 20 is made of a biodegradable or compostable material that can be, for example, wool, silk, cotton, flax, hemp, jute, sisal, raffia, ramie.

Complementary thread 20 may be a discontinuous or continuous filament, in the latter case it may be a single filament continuous thread or a multifilament continuous thread. The filament or filaments can be flattened filaments or textured filaments.

Nevertheless, in the case of continuous complementary threads 20, FIG. 7 only shows a substantially parallel arrangement in which the complementary threads 20 and elastic fibers 10 are parallel to each other. However, for example, a wrapped arrangement in which the complementary thread 20 forms a sheath around the elastic fiber 10, as well as an interconnected arrangement in which connection points are provided between the complementary thread 20 and the elastic fiber 10 at a predetermined distance from each other. The invention is not limited by this exemplary embodiment, as different arrangements between the complementary threads 20 and the elastic fibers 10 are possible.

It is an elastic core thread that falls within the scope of the present patent application and is produced by the method described above, as well as an elastic fabric containing such an elastic core thread.

The foregoing described exemplary embodiments of the invention will fully clarify the invention according to the conceptual aspects, so that others can easily understand it without further study and by applying current knowledge. Such embodiments may be modified and/or adapted for various uses without departing from the invention, and such adaptations and modifications should therefore be considered equivalent to the particular embodiments. It should be understood that The means and materials for realizing the different functions described herein may have different properties for this reason without departing from the field of the invention. It is to be understood that the expressions or terminology employed herein are for purposes of description and not of limitation.

Claims (13)

A method for producing an elastic core yarn (50), comprising:
A step of pre-arranging a source (51) of an elastic core (30) containing elastic fibers (10) made of natural rubber containing more than 80% of cis-1,4-polyisoprene, the step comprising: 10) has a linear mass density set between 200 dtex and 1000 dtex;
- pre-positioning at least one covered yarn (40) comprising cotton at a weight percentage of more than 50%;
The covered yarn has a linear mass density set between 6Nm and 100Nm,
pre-positioning, wherein the covered yarn (40) is twisted with an initial twist direction selected between "Z" and "S";
- conveying the elastic core (30) and the covered thread (40) at their respective predetermined conveyance speeds to a collection spool (70);
The conveyance speed of the elastic core (30) is
- From the initial velocity of the elastic core (30) at the supply source (51),
- ranging up to a final velocity of at least twice the initial velocity at the collection spool (70);
the conveying step is carried out in such a way that the covered thread (40) laterally reaches the vicinity of the elastic core (30) in the winding space (35);
- winding the covered yarn (40) helically around the elastic core (30) in the winding space (35), thus obtaining the elastic core yarn (50);
The conveyance speed is such that in the step of spirally winding,
- such that the covered yarn (40) is twisted in a final twist direction opposite to the initial twist direction, i.e. between "S" and "Z", respectively;
- The number T of coils of the covered yarn (40), which is set between a predetermined minimum value _T0 and a predetermined maximum value _T1 according to the linear mass density Nm, is determined by the elastic core yarn (50). is selected to be wrapped around one length unit of
The wrapping space (35) is a protected space surrounded by a container (67),
The linear mass density Nm is a metric number that defines the length of the covered yarn per 1 kg in Km/Kg, the minimum value T0 _is the minimum number of coils of the covered yarn, and the maximum value T ₁ is the maximum number of coils of the covered yarn;
The minimum value T ₀ and the maximum value T ₁ respectively correspond to the linear mass density Nm shown in the respective rows of the table below (Table 1), and

If the value of said linear mass density Nm is intermediate between the values shown in each successive row of said table, said minimum and maximum values T ₀ , T ₁ are determined by said respective successive rows of said table; and by linear interpolation of said values written respectively in columns starting with T ₀ and T ₁ . For each value of the linear mass density Nm, the number T of coils per unit of length is determined by the following formula:
T=KN _m ^0.425
has the value provided by
The method according to claim 1 , wherein K is a numerical value set between 75 and 290. Specifically, the method according to claim 2 , wherein K is set between 90 and 250. More specifically, the method according to claim 2 , wherein K is set between 120 and 220. 2. The method according to claim 1, wherein the covered yarn (40) is selected among single-layer yarns, double-layer yarns, and yarns with three or more layers. The step of conveying the elastic core (30) and the covered thread (40) to the collection spool (70) comprises:
- The elastic core (30) and the covering yarn (40) are passed through the longitudinal through-hole (63) of the rotating hollow cylinder (61), which rotates at a predetermined rotational speed, and along the side surface (62). said longitudinal through cavity (63) having an inlet end opening (68) and an outlet end opening (69) for said elastic core (30);
- the elastic core (30) and the covering yarn (40) are placed facing the outlet end opening (69) of the longitudinal through cavity (63) of the hollow cylinder (61) at a predetermined distance therefrom; passing through an orifice (66) that
The wrapping space (35) is set between the outlet end opening (69) and the orifice (66), so that the container (67) is connected to the orifice (66) and the elastic core (30). 2. The method according to claim 1, having an exit passageway in ), the covering thread (40) passing as the elastic core thread (50) through the orifice (66). The source of the elastic core (30) is a spool (51) comprising a central hub (53) having a hub radius (r) and an end flange (54) having a flange radius (R); 51) is arranged rotatably about its own first axis (52), said step of conveying said elastic core (30) unwinding said elastic core (30) from said spool (51). including the step of reverting
an intermediate balance cylinder (56) having a predetermined radius (P) longer than the flange radius (R) shortened by the hub radius (r) is a fixed cylinder parallel to the first axis (52); a second axis (57) thereof and arranged in contact between said spool (51) and a motion distribution shaft (58) parallel to said first and second axes (52, 59); is,
2. A method according to claim 1, whereby the elastic core (30) is maintained in contact with the intermediate balancing cylinder (56) during the unwinding step. The elastic fiber (1) also contains the following components:
- a vulcanizing agent that is sulfur with a weight concentration in the natural rubber set at 0.5% to 3.0%;
・Vulcanization accelerator and vulcanization activator,
・Anti-stick agent and
・Antioxidants and
・Contains a stabilizer,
2. The method according to claim 1, wherein said elastic fibers (1) are obtained from longitudinally cut flat threads of said natural rubber such that said elastic fibers (1) are obtained in the form of elastic filaments having said linear mass density. Method described. The method of claim 1, wherein the elastic core (30) comprises complementary threads (20) disposed along the elastic fibers (10). 10. The method of claim 9 , wherein the complementary thread (20) is made of biodegradable material. 11. The method of claim 10 , wherein the biodegradable material is selected from the group consisting of wool, silk, cotton, flax, hemp, jute, sisal, raffia, ramie. The complementary thread (20) is
- a parallel arrangement in which the complementary yarn (20) is arranged parallel to the elastic fiber (10);
- an interconnected arrangement in which said complementary threads (20) have connection points to said elastic fibers (10), said connection points being arranged at a predetermined distance from each other;
a continuous yarn having an arrangement along said elastic fibers (10) selected from the group consisting of: a wrapped arrangement, in which said complementary threads (20) form a covering around said elastic fibers (10); 10. The method of claim 9 , wherein: 13. The method of claim 12 , wherein the complementary yarn (20) is selected between a single-filament continuous yarn and a multi-filament continuous yarn, including flattened or textured filaments.

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